1. Field of the Invention
This invention relates to semiconductor fabrication processes, and more particularly, to a method for cleaning the slurry remnants left on a polishing pad after the completion of a chemical-mechanical polish (CMP) process conducted for global planarization of a semiconductor wafer.
2. Description of Related Art
In the fabrication of semiconductor products, such as CPUs and various memory devices, the CMP technique is a global planarization process which can a provide flat and polished surface for a semiconductor wafer. It is currently the only semiconductor technology that can provide a global planarization of semiconductor wafers.
In a CMP process, the surface of the wafer that is to be polished (hereinafter referred to as the process surface of the wafer) is placed upside down on a polishing pad on a CMP machine. The polishing pad can be rotated so as to rub against the process surface of the wafer. During the CMP process, a chemical agent, which is customarily referred to as a slurry, is applied on the wafer to assist the polishing pad in polishing the process surface of the wafer.
The slurry can be a mixture of colloidal silica, dispersed alumina, and an alkaline solution, such as KOH or NH.sub.4 OH or CeO.sub.2 base slurry. The colloidal silica and dispersed alumina particles, which are highly abrasive in nature can help to polish the process surface of the wafer on the polishing pad.
After the completion of each CMP process, the slurry remnants left on the polishing pad should be cleaned away prior to conducting a subsequent CMP process on another wafer. One conventional method of cleaning the slurry remnants left on the polishing pad after the completion of a CMP process is depicted in detail in the following with reference to FIGS. 1A and 1B.
Referring to FIG. 1A, there is shown a polishing pad 10 after the completion of a CMP process. This polishing pad 10 has been treated by a pad dresser (not shown). After the CMP process, a large amount of slurry remnants 12 are left on the polishing pad 10, which should be cleaned away before another wafer can be placed and polished on the polishing pad 10. To remove the slurry remnants 12, a stream of deionized water 14 is jetted on the polishing pad 10 so as to clean away the slurry remnants 12 left on the polishing pad 10.
One drawback to the foregoing method, however, is that it is not effective at thoroughly cleaning away all of the slurry remnants 12 left on the polishing pad 10. As shown in FIG. 1B, a small amount of the slurry remnants 12 may still remain on the polishing pad 10. When these uncleaned slurry remnants 12 dry out, they could cause scratches to the subsequent wafers that are placed on the polishing pad 10 to undergo a CMP process. This will significantly affect the wafer yield rate.